High voltage terminal construction and method of assembly



F. S. SMITH May 8, 1934.

HIGH VOLTAGE TERMINAL CONSTRUCTION AND METHOD OF ASSEMBLY Filed Deo. 14, 1931 Farr/riva.

Patented May 8, 1934 iUNITED STATES PATENTI--FF1CE HIGH VOLTAGE TERMINAL CONSTRUCTION AND METHOD OF ASSEMBLY 19 Claims.

This invention relates to high Voltage terminal construction and method of assembly thereof.

One of the objects of this invention is to provide a thoroughly practical, simple and inexpensive terminal construction well adapted to function at high voltages and to provide a method of relating such a terminal to the tank, container or casing that houses the high voltage apparatus in a manner that is simple, thoroughly practical, and well adapted to meet the peculiar requirements of practical use. Another object is to provide a terminal construction of the above mentioned nature adapted to withstand relatively high diiferences of pressures between the outside l5 and inside thereof and to achieve a construction in which danger of leakage of dielectric is dependably precluded. Another object is to provide a high voltage terminal construction adapted to function in coaction with a tank or con- 20 tainer containing the high voltage apparatus immersed in a gaseous dielectric under high pressure and to provide a method and apparatus for reliably and dependably achieving a sealed joint or connection between the terminal construction and the container, all without detrimentally affecting the electricgor other characteristics or' qualities of the apparatus contained within the tank or container. Another object is to provide a construction of the above mentioned character in which assembly and disassembly thereof may be reliably and dependably achieved while making certain that in assemblysealed joints or connections are quickly and dependably achieved. Other objects will be in part obvious or in'part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements, arrangements of parts and in the several steps and relation and order of each of the same to 40 .one or more of the others all as will be illustratively described herein, and the scope of the application of -which will be indicated in the following claims.

In the accompanying drawing in which is shown a preferred embodiment of my invention.

Fig. 1 is a vertical central, sectional view of a high voltage terminal construction related to its tank or containenand Fig. 2 is an enlarged vertical central sectional view of the upper part of the terminal construction virtually as seen in Fig. 1.

Similar reference characters refer to similar parts throughout the several views of the drawing. Referring now to the drawing and more particularly to Fig. I have shown a container l0 preferably of cylindrical form and preferably made of pressed steel so as to insure its withstanding substantial diferences of pressure between the interior and exterior thereof. When l made of pressed steel the container 10 may and preferably does have its bottom 10a formed integrally therewith. The container is adapted to be closed by an end shell or closure member l1 also preferably made of pressed steel and shaped so as C5 to be received within the upper open end of the container or tank 10; the closure member 11 is curved adjacent its peripheral portions so that the upper peripheral portions 10b of the container l0 may thereafter be bent over onto the ./0 closure or shell 1l and the parts 4then welded together as at l2, thus insuring a mechanically small construction and one that is hermetically sealed.

Within the container l0 is mounted and sup- 75 ported in any suitable manner the high voltage apparatus which may take any form, and' solely by way of illustration I have indicated in the drawing a transformer as comprising the apparatus within the sealed container. This transformer I haveindicated purely diagrammatically and it may comprise a low voltage winding 13, connection to which may be made from the exterior through any suitable terminal construction sealed into a suitable portion of thewalls of the enclosing container; this (terminal construction may take the form, for example, shown in my copending application Serial No. 511,309, filed J anuary 26, 1931,- now Patent No. 1,907,599.

The transformer has a high tension winding 14 90 one or both of the terminal connections of which may be brought out through the high voltage ter- `minal construction which includes certain features of my invention and which will be described in detail hereinafter. Illustratively, however, I

` have shown one end of the high voltage winding 14 as being grounded to the tank 10-11 in any suitable way and at any suitable point; diagrammatically this one terminal is grounded by conductor 15 to the container 10 so that it will suice 100 to describe in detail how -the other terminal of the high voltage winding 14 is brought out through the casing and insulated therefrom.

I first provide an opening of suitable size in a suitable portion of the closure and illustratively I have shown that opening as of circular shape and positioned centrally and hence coaxially of the closure member 11. Into thisopening is snugly tted, from the interior thereof (before the assembly of the closure 11 to the tank 10) a col- 110 leo Collar 16 isinteriorly stepped or turned down to provide a shoulder 1Gb and a second shoulder 16e, and drilled into the shoulder 16b and aligned about a circle is a plurality of holes ldthat extend parallel to the axis of the collar 16; these holes 16d are tapped so that they may later receive suitable securing screws.

The upper portion of the collar 16, as viewed in Fig. l, is bored out and i-s threaded; this thread may be of any suitable construction and it may,' if desired, be somewhat tapered, approximating in that respect a pipe thread.

Collar 16, as will be pointed out in detail hereinafter, is to support, at its threaded portion, the high voltage terminal construction.

But interfitted with the interior shoulder or stepped portions of Athe collar 16 is an annular member 18, preferably of metal, and provided with an annular rib or lip 18a adapted to rest against the shoulder 16e of the collar 16 and adapted to snugly fit into and to be centered by the cylindrical wall adjacent the shoulder 16e.

Projecting to the right of the rib 18a is a flangelike portion 18h which overlaps the shoulder 1Gb, and passing through-the ange 18h are suitable screws 19 that are received in the threaded holes 16d of the collar 16, thus to hold the annular member 18 in place.

The latter has an inwardly and upwardly directed lip 18e which, as appears clearly from Fig. 1, extends upwardly into substantial parallelism with the annular rib or lip 18a but extends upwardly beyond the latter so as to be positioned interiorly of but parallel to the upper and inner threaded portion of the collar 16, all for a purpose to be more clearly described hereinafter. The upper end of the inner lip 18e is tapered as at 18d.

The electrical apparatus within the tank 10-11 is immersed in a gaseous dielectric under relatively high pressure, forv example, in a gas like nitrogen under a pressure on the order of 15 atmospheres. The coaction of this gaseous dielectric under pressure with various parts of the high voltage apparatus, illustratively the transformer 13-14, need not here be dealt with but it may be pointed out that the maintenance of the difference of pressure between the inside and the outside of the casing or container must be maintained not only to insure the intended functioning of the high voltage electrical apparatus but also of the preferred form of high voltage terminal construction that I prefer to employ.

This terminal construction includes a tube-like housing 20 of solid dielectric material, Such as phenolic condensation product, and it is made of substantial thickness not only to achieve certain coactions in insulating the high voltage conductor but also to withstand the difference of pressure between the interior and exterior thererof. Preferably the housing 20 is somewhat tapered, being conveniently and illustratively proportioned somewhat as is shown in Fig. l.v

At its upper endV the housing 20 is internally threaded as at 20a, these threads being preferably molded into the member 20 when the latter is formed, and threaded into the upper end of member 20 is a plug 21 (see also Fig.2), the lower end of which is bored out but tapered as at 21a to snugly -receive and holdfa tapered plug 27 to which is secured a tubular conductor 22, the latter being secured in place in a'manner described more clearly hereinafter, and being thus held coaxially with the member 20; as appears from Fig. 1,- the member 22 extends downwardly to a substantial extent where it coacts with a metal bushA ing 23 with respect to which it is likewise held coaxially.

The sleeve-like insulating member 20 is interiorly threaded at its lower end as at 20h, these threads being also preferably formed'during the process of molding the member 20, and it is with the threads 20h that the upper outer threaded portion of the metal sleeve-like bushing 23 coacts. The threaded connections between the upper plug 21 and the housing 20 and between the latter and the bushing 23 are not only of suilicient mechanical strength to withstand the difference of pressure between the inside of the construcconnect once the airtight joint or joints has or have been made.

The inner cylindrical wall or face 23a of ,bushing 23 will be seen to be spaced from the high tension conductor 22 and, moreover, the radii of curvature lof this inner face and of the tubular conductor or lead 22 are such that the ratio therebetween is equal to or less than 2.718, forming thus a Vfast discharge gap lled with the gaseous dielectric under high pressure, which gap will break down instantaneously at a certain voltage and, moreover, will break down without the breakdown being preceded by corona. The critical breakdown Voltage of this fast discharge gap is such that the gap breaks down when a voltage greater than that which the electrical apparatus within the container can safely withstand is imposed upon the high voltage circuit or lead 22. Preferably the upper and lower interior ends 23h and 23e of the bushing 23 are rounded at preferably a relatively large radius of curvature to prevent undesirable flux concentration at these points and thus to prevent interference with the functioning of the fast discharge gap above de- The lower end of bushing 23 is threaded as at n 23d to mate with the threaded part of the collar 16, and it is also provided with an axially directed annular recess 23e into which the flange or lip 18e of the member 18 is received as the bushing 23 is threaded down into the collar 161 The bushing 23 is provided with a laterally directed flange 23f preferably provided withperipheral openings 24 and 25 adapted to receive the prongs or studs of a spanner wrench so that the bushing 23 with the terminal construction carried thereby may be threaded into the collar 16 and'a substantial rotating force or energy exerted thereon.

In assembling the terminal construction with respect to the casing 10-11 and the electrical apparatus therein contained, either initially or after disassembly had subsequently taken place, a suitable conductor 26 is led from the terminal end of the high voltage apparatus (high voltage winding 14, for example) and threaded upwardly through the tubelike conductor 22, whence (see particularly Fig. 2) it is passed through the hollow tapered plug 27, thence outwardly through the bore of the plug 2l.

The threaded portion 23d of the bushing 23 and the threaded part of collar 16 are coated or tinned with a layer, of suitable thickness, of a suitable vsealing alloy which, by way of example,

may be an alloy known as amaloy which consists of about 98% of lead, approximately 2% oi tin, and the remainder, a small fraction of 1%, of phosphorus.

The terminal construction, with the conductor 26 threaded completely therethrough, is now ready to be assembled to the collar 16 and hence to the casing 10-11. The threaded portions of the bushing 23 and collar 16 are interengaged, the spanner wrench applied to the projecting flange 23j by engaging it with the openings 24-25, and the rotation of the bushing 23 with its supported construction commenced.

As the rotation proceeds, the tight interfitting of the threaded parts or of the threads, made tighter by the coated alloy on one or both of these threaded parts, produces such a resistance to turning that a substantial quantity of heat is generated at the threads andthe alloy virtually fuses or melts, the rotation ofthe bushing 23 proceed-s ing until the bushing is sufficiently driven home, whereupon the cooling off of the parts results virtually in a hermetic sealing of the parts together.

' During the threading of the bushing 23 into the collar 16 and the resultant fusing or melting of the alloy, it is possible that some of the fused alloy is sufficiently released to cause it to drop away from the joint being formed. Ii any such particles of this alloy are allowed to enter the casing 10-11, the electrical properties oi? the apparatus contained therein might be very detrimentally affected; for example, short circuits might be caused or, if there is included in the container a dielectric material such, for example, as ground fused quartz or ground Pyrex glass, as is disclosed in my copending application Serial No. 580,908, filed December 14, 1931, these particles of the alloy would intermingle therewith and badly affect if not entirely destroy its insulating properties throughout at least certain portions thereof.

But as thebushing 23 is threaded downwardly, as viewed in Fig. 1, any such particles of the alloy that might drop from the joint being formed are caught in the annular space between the lips 18a -and'lcof the member 18. Furthermore, these particles are permanently entrapped so that even though the apparatus were to be inverted from the position shown in Fig. 1, such particles could not escape. This latter action is achieved not only by virtue of the tight t of the lip or ange 18a with the interior of the collar 16 but also by the interiitting and interlocking of the inner and upwardly elongated lip or flange 18e with the lower part of the bushing 23, into the annular recess 23e of which this lip enters and tightly interflts, this entry being facilitated by the tapered peripheral portion 18d of the lip 18e. Thus I am enabled .toachieve a dependable seal between these metallic parts and to prevent the sealing operation and/or materials used therein from interfering with the ultimate action of the apparatus sealed within the container.

, Having driven the bushing 23 with the parts carried thereby home, the conductor -26`may now beanchored at its upper end (see Fig. 2) and the hollow plug 2l sealed. This maybe achieved by theY following construction:-

'Ihe metal ltube or conductor 22 is secured to the lower end of the hollow tapered plug 27 in any suitable manner; the latter is interiorly threaded to receive a hollow screw 29 whose head 29a abuts againstan inside shoulder 2lb of the plug member 2l; itis by the screw 29 that the tapered plug 27 is drawn up into the tapered bore 21a of the plug 2l and thus securely held in place, and it is also through the hollow screw 29 that the conductor 26 is initially threaded.

The upper end of the plug 2l is closed by hollow plug 33 which may be secured in place in any way, as by threading, and through this plug also the conductor 26 -is threaded. The conductor 26, after the assembly of the terminal construction as above described, is now drawn sufliciently taut, is cut off substantially ilush with the upper end of the plug 2l and its short end is then bent over in any suitable way onto the upper surface of theplug 33.

Then there is inserted a suitable sealing means such as a plug 35 of lead, which is inserted on top of the bent over end of the conductor 26 and this lead plug may then be hammered out or expand- -ed laterally in any suitable way. Thereupon a plug 34 is threaded into the remaining portion of the reduced upper end bore of the plug 21 and is driven home, additionally tightly compressing the lead plug 35 and thus hermetically sealing -the bore of the plug 2l against the escape of the gaseous dielectric under pressure within the cas ing 10--11 and within the terminal construction. If desired, the joint between plug 34 and part 2i may be soldered.

The upper outer end of the plug 2i, which' projects beyond the upper end of the housing 26, may be threaded to receive any desired means-such as a nut or the like, with which to electrically. conneet the exterior circuit in coaction with which the high Voltage apparatus or device within the casing 10-11 is to function.

The gaseous dielectric under pressure may be injected into the casing and hence also into the interior of the terminai construction by any suitable means (not shown).

Should it become necessary to disassemble the construction, the gaseous dielectric under pressure may first be released in any suitable way or it may be released through the hollow plug 21. First the screw plug 34 is removed, then the lead sealing plug 35, whereupon the conductor 26 is sufciently released so that the entire terminal construction may be rotated, to disconnect the threaded bushing 23 from the collar 16, without rotating and twisting the conductor 26. During this unscrewing action, the device 18 again acts to prevent any of the sealing alloy that might be melted or otherwise dropped from the threaded portions as a result of the unthrea'ding of the parts from falling into the casing 101i`..-

As above pointed out, the parts 22 and 23 form a fast discharge gap. The member 18 (Fig. 1) is preferably of metal but its eiectve diameter or radius, with respect to the radius of the rigid conductor 22, is suiciently greater than the radius of the cylindrical surface 23a of the bushing 23 to prevent spark-over, through the gaseous dielectric under pressure, between the part 18 and the part 22. Moreover, the member 18 is, throughout the portions exposed toward high voltage no v parts, given a'curvature of relatively great radius so as to avoid concentration of flux and so as further to reduce the possibility of undesired spark-over thereto from high voltage parts of the apparatus.

-Depending upon various facts, the hermetic sealing of the threaded joint between the parts 16 and 23 may be carried on, as desired, either by achieving an actual fusing of the alloy, thus to solder the parts together, or simply by the cold flow of the alloy; in the former case sufficient heat is made effective at the joint to cause melting of the alloy while in the latter case the achievement of such heat at the joint may be dispensed with. Where it is undesired or impracticable to provide the necessary heat, the cold relatively soft metal, illustrativelyl the above-mentioned alloy, is made to ow cold under the confinement thereof by the threads of the parts and the pressure or forces exetd thereon. In either of the abovementioned cases, the device 18 and particularly the coaction therebetween and the bushing 23 achieve a dependable and effective mechanical seal as against the entry into the sealed container 10-11 of particlesof the sealing metal that would otherwise drop into the casing; moreover, these features of construction and coaction also prevent the entry into the casing of particles or parts of the threaded members 16 and 23 that might lbe dislodged therefrom or sheared off in the course of the interthreading of these parts. Moreover, it will be seen that this mechanical seal has a dependable and wide range of action throughout and in spite of the relative movement that takes place between the collar 16 and the bushing 23 as the latter is threaded into the former.

While I have above specifically mentioned a preferred form of sealing alloy, I wish it to be understood that any other suitable alloy or suitaable metal may be employed in its stead and I do not Wish to be limited to the specific alloy illustratively above disclosed, nor do I wish to be limited to a sealing metal or alloy having the specific melting point of the alloy above mentioned.

It will thus be seen that there has been provided in this invention a construction and method of assembly in which the various objects hereinbefore noted together with many thoroughly practical advantages are successfully achieved.

As many possible embodiments may be made of the mechanical features of the above invention and as the art herein described might be varied in various parts, all Without departing from the scope of the invention, it is to be understood that all matter hereinabove set forth or shown in the accompanying drawing is to be interpreted as illustrative and not in a limiting sense.

I claimz- 1. In high voltage terminal construction, in combnation, a member having a threadedbpening through which a conductor is to be passed, a terminal construction having a bushing threaded at one end for coaction with said member and having sealed thereto a solid dielectric housing having a conductor sealed through its remote end, one of said threaded parts having a soft metal applied to the threads thereof, and means in sealed connection with said first mentioned member and having a part adapted to engage said bushing as the latter is threaded into said opening for entrapping metal particles disengaged from the parts being interthreaded.

2. In high voltage terminal construction, in combination, a' member having a threaded opening through which a conductor is to be passed, a terminal construction having a bushing threaded at one end for coaction with said member and having sealed thereto a solid' dielectric housing having a conductor sealed through its remote v end, said threaded parts being. proportioned tightly to intert, and means carried by said first mentioned member and projecting inwardly about the region of the threaded part thereof for catching metal particles disengaged from the parts being interthreaded.

.3. In terminal construction, in combination, a casing having therein an electrical apparatus and having a threaded opening, means projecting from the wall of said casing into said opening, an insulating terminal construction having a threaded bushing adapted to be threaded into said opening, said bushing having an annular recess into which said projecting means fits as the bushing is threaded into the opening.

4. In terminal construction, in combination, a

casing having a threaded opening and annular means of less diameter than the diameter of the threaded opening, said annular means projecting in alignment with the axis of said opening, and an insulating terminal construction including a threaded bushing adapted to be threaded into said threaded opening, said bushing having an annular recess into which said annular means is received upon said bushing being threaded into said opening.

5. In terminal construction, in combination, a casing adapted to receive an electrical apparatus and having an opening therein, a threaded collar secured in said opening, an insulating terminal construction including a threaded collar and insulating means associated'therewith, said collars being adapted to be interthreaded, and an annular ange projecting from one of said collars, the other of said collars having an annular recess into which said flange is received to form a sealed enclosed space about those threaded portions of said collars that are otherwise exposed toward the interior of said casing.

6. In terminal construction, in combination, a casing adapted to receive an electrical apparatus and having an opening therein, a threaded collar secured in said opening, an insulating terminal construction including a threaded collar and insulating means associated therewith, said collars being adapted to be interthreaded, a part projecting from one of said collars and into the path of movement of the other, and means on the other collar adapted to intert with said projecting means to form an enclosure about the threaded portions of the collars that are otherwise exposed toward the interior of said casing.

7. In terminal construction, in combination, a casing adapted to receive an electrical apparatus and having a threaded opening therein, metallic means in sealed connection with said casing and extending about said opening and providing a ange of lesser diameter than said opening and extending parallel to the walls of the latter, a terminal construction comprising a threaded bushing adapted to bethreaded into said opening and carrying insulating means which supports a conductor concentrically with said bushing, the

v radii of curvature of said conductor and of said bushing being proportioned so as to form a fast discharge gap, said bushing being shaped to form a substantially sealed connection with said flange l said metallic means having a radius of curvature sufficiently great to prevent interference thereby with the actiorr` of said fast discharge gap.

8. In terminal construction, in combination, a casing adapted to receive an electrical apparatus and having a threaded opening therein, metallic means in sealed connection with said casing and extending about said opening and providing a flange of lesser diameter than said opening and extending parallel to the walls of the latter, a terminal construction comprising a threaded bushing adapted to be threaded into said opening and carrying insulating means which supports a conductor concentrically with said bushing, the radii of curvature of said conductor and of said bushing being proportioned so as to form a fast discharge gap, said bushing being shaped at its lower end to telescope with said flange as said bushing is threaded into said opening, the effective radius of curvature of said metallic means being greater than said radius of curvature of said bushing.

9. In terminal construction, in combination, a casing adapted to receive an electrical apparatus and having a threaded opening therein, metallic means in sealed connection with said casing and extending about said opening and providing a flange of lesser diameter than said opening and extending parallel to the walls of the latter, a terminal construction comprising a threaded bushing adapted to be threaded into said opening and carrying insulating means which supports Ythreaded wall and insulating plied thereto prior to a conductor concentrically with said bushing, the radii of curvature of saidvconductor and of said bushing being proportioned so as to form a fast discharge gap, said bushing having an annular recess adjacent its lower portion within which said flange is received as saidbushing is threaded into said opening.

10. In terminal construction, in combination, a casing adapted to receive an electrical apparatus and having an opening therein whose wall is threaded, an insulating terminal construction including a metal member having an external means associated therewith, one of said threaded walls havingapassembly ofthe parts a metallic sealing alloy, and means for preventing alloy dislodged by the interthreading of said parts from dropping into said casing.

l1. In terminal construction, in combination, a

' casing adapted to receive an electrical apparatus and having an opening therein whose wall is threaded, an insulating terminal construction including' a metal member having an external threaded wall and insulating means associated therewith, one of said threaded walls having applied thereto prior to assembly of the parts a metallic sealing alloy, and means completely enveloping those portions of the threaded joint that are exposed interiorly of said casing for entrapping alloy particles disengaged from the parts being interthreaded.

12. In terminal construction, in combination,

a casing adapted to receive an electrical apparatus and having an opening therein whose wall is threaded, an insulating terminal construction including a metal member having an external threaded wall and insulating means associated therewith, one of said threaded Walls having applied thereto prior to assembly o the parts a metallic sealing alloy, and means associated with one of said threaded parts and telescoping with the other for entrapping alloy particles dislodged at those portions of the'threaded joint that are exposed interiorly of said casing.

i3. In terminal construction, Vin combination, a casing adapted to receive an electrical apparaus and having an opening therein whose wall is threaded, an insulating terminal construction including a metal member having an external threaded wall and insulating means associated therewith, one of said Athreaded walls having applied thereto prior to assembly of the parts .a meallic sealing alloy, and means in sealed connection with the inside wall of said casing and forming a joint with said metal member as the latter is threaded into said opening for entrapping alloy particles disengaged from the parts being interthreaded.

lll. The method of sealing a terminal construction having a threaded metal part onto a casing having a threaded part which consists in applying to at least one of said threaded parts an alloy of low melting point, and utilizing the heat generated during the interthreading of said threaded parts to cause the alloy to flow.

15. The method of sealing a terminal construction having a lthreaded metal part onto a casing having a threaded part which consists in rst applying a sealing metal to the threads of one of said parts, interthreading said parts, and entrapping particles of the sealing metal dislodged by the interthreading of said parts.

i6. The method of sealing a terminal construction having a threaded metal part onto a casing having a threaded part which consists in applying a metallic sealing \means to one of said threaded parts and interthreading the latter while maintaining a mechanical seal of the joint exposed interiorly of said casing against the dropping into the casing of dislodged particles of the metallic sealing means.

17. In terminal construction, in combination, a casing having a threaded part, a terminal construction having a threaded part, and means maintaining a mechanical seal against the passage of solid particles about those portions of the threaded parts that are ,exposed to the interior of said casing. A

18. In terminal construction, in combination, a casing having a threaded part, a terminal construction having a threaded part, and means` forming an extensible seal against the passage of foreign particles from those portions` of the threaded parts exposed to the interior of said casing. 

